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782.cpp
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782.cpp
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class Solution {
public:
int movesToChessboard(vector<vector<int>>& board) {
int n = board.size();
for (int i = 0; i < n; ++i) {
for (int j = 0; j < n; ++j) {
if ((board[0][0] ^ board[i][0] ^ board[0][j] ^ board[i][j]) == 1) return -1;
}
}
int rowSum = 0;
int colSum = 0;
int rowSwap = 0;
int colSwap = 0;
for (int i = 0; i < n; ++i) {
rowSum += board[0][i];
colSum += board[i][0];
// assume 101010...
if (board[i][0] == (i % 2)) rowSwap++;
if (board[0][i] == (i % 2)) colSwap++;
}
if (rowSum != n / 2 && rowSum != (n + 1) / 2) return -1;
if (colSum != n / 2 && colSum != (n + 1) / 2) return -1;
if (n & 1) {
if (rowSwap & 1) {
rowSwap = n - rowSwap;
}
if (colSwap & 1) {
colSwap = n - colSwap;
}
}
else {
rowSwap = min(rowSwap, n - rowSwap);
colSwap = min(colSwap, n - colSwap);
}
return (rowSwap + colSwap) / 2;
}
};